Solar greenhouse vegetable fields have been found to be hotspots of nitrous oxide (N₂O) emissions in China, mainly due to excessive manure application and irrigation. Pulses of N₂O emissions have been commonly reported by field monitoring works conducted in greenhouse fields, though their significance regarding total N₂O emissions and the driving mechanism behind them remain poorly understood. N₂O fluxes were monitored in situ using a static opaque chamber method in a typical greenhouse vegetable field. Then, laboratory incubations were conducted under different soil moisture and manure application gradients to monitor nitrous oxide emissions and related soil properties, using a robotized incubation system. Field monitoring showed that the occurrence of clear N₂O emission bursts closely followed fertilization and irrigation events, accounting for 76.7% of the annual N₂O efflux. The soil N₂O flux increased exponentially with the water-filled pore space (WFPS), causing extremely high N₂O emissions when the WFPS was higher than 60%. During the lab incubation, emission bursts led to N₂O peaks within 40 h, synchronously changing with the transit soil NO₂⁻. An integrated analysis of the variations in the gas emission and soil properties indicated that the denitrification of transit NO₂⁻ accumulation was the major explanation for N₂O emission bursts in the greenhouse filed. Nitrous oxide emission bursts constituted the major portion of the N₂O emissions in the Chinese greenhouse soils. Nitrite (NO₂⁻) denitrification triggered by fertilization and irrigation was responsible for these N₂O emission pulses. Our results clarified the significance and biogeochemical mechanisms of N₂O burst emissions; this knowledge could help us to devise and enact sounder N₂O mitigation measures, which would be conducive to sustainable development in vegetable greenhouse fields.

Soil aggregates and organic matter are considered to be important indicators of soil quality. The objective of this study was to determine land-use effects on the distribution of soil organic carbon (SOC) associated with aggregate-size fractions. Bulk soil samples were collected from incremental soil depths (0–10, 10–20 20–40, 40–70, and 70–100 cm) under three land-use types: fruit tree orchards established in 1987, cropland, and forage field. Soil samples collected from these plots were analyzed for aggregate stability after wet sieving into four aggregate-size classes (>2000, 250–2000, 53–250, and cropland > fruit tree orchard. Aggregate stability was greater in cropland and forage field than under fruit tree orchards. Soil organic C decreased with increasing soil depth but was greater under fruit tree orchards than others and was mainly concentrated in the topsoil layer (0–20 cm). Sieved fraction (<53 μm) had a greater SOC concentration, regardless of soil depth or land use. Our data supported the hypothesis that perennial vegetation (fruit tree orchard) and the proportion of aggregates with diameter <53 μm are suitable indicators of SOC accumulation and may therefore have a greater potential for SOC sequestration than the cropland.